Vehicle engines typically include a drive pulley attached to a crankshaft, and at least one accessory having an accessory pulley. The accessory may include, for example, an Air Conditioning compressor, a power steering pump, an alternator, an air pump, or some other device that is driven by a rotational input. An endless rotatable device, e.g., a serpentine belt, connects the drive pulley with accessory pulleys. The drive pulley rotates the endless rotatable device. The endless rotatable device in turn rotates the accessory pulleys to power the accessory devices. Accordingly, the endless rotatable device transmits rotation from the drive pulley to the accessory pulleys to drive the accessories. As the rotational speed of the crankshaft increases, the rotational speed of the drive pulley increases, because the drive pulley is directly connected to the crankshaft. Many of the accessories are designed for optimal operation when the engine is operating at an idling speed. Operating the accessories at higher rotational speeds increases energy losses associated with the accessories.